Having issues with action on this pbass I built. The lowest I can get that fat string without buzzing is still too high, I have the truss rod backed off as much as possible and the strings are VERY tense (130-65 tuned DGCF). Too much tension for most players but fine for me. Theres a fair bit of relief but it seems to not be enough, but I can't get anymore. I'm not THAT experienced with setups, my understanding is that to eliminate fret buzz with low action is to increase relief, but like I said I can't back the truss rod off anymore, and more string tension than I've already got would probably be dangerous. Any ideas? Additional: the neck has a big shim in it as I had bottomed out the bridge before getting low enough action on that string. After shimming it was better but I still can't get it low enough without it just buzzing out awfully. It can't be the limitation of the string as I've played 5 strings with low action and no issues with that B.